Tree tannins can tame manure odor

WASHINGTON – Foul odors from manure pits have made uneasy neighbors of agriculture operations and nearby communities. But the US Dept. of Agriculture may have found a new option for odor control.

A USDA study found that tannins from the quebracho tree can control the production of odor-causing compounds in manure. Quebracho, a name in Spanish used to describe very hard-wood trees. Tannins can be extracted from both red and white quebracho.

Researchers with the Agricultural Research Service in Peoria, Ill. conducted a study to determine if quebracho tree tannins could suppress odor-generating bacteria in manure. The ARS researchers drew on other studies that found tannins naturally present in tree leaves and other feed items can block bacterial activity in the guts of ruminant livestock.

Scientists incubated swine manure under laboratory conditions designed to mimic on-farm conditions. Seven days after adding quebracho tree tannins to the manure, scientists found that hydrogen sulfide and methane production had declined more than 90 percent and that production continued to drop for another three weeks. Sulfate-reducing bacteria dropped 70 percent to 90 percent. Hydrogen sulfide and other sulfur compounds comprise roughly half of the offensive odorants from swine manure, according to ARS.

ARS said if field studies are successful, quebracho tree tannins may provide swine producers a cost-effective and environmentally friendly option of controlling odors and greenhouse gases.